(i) Field of the Invention
This invention relates to emulsion-type or solid cut meat products, prepared containing stabilized cooked cured-meat pigment or encapsulated powdered cooked-cured meat pigment which is related to a non-nitrite meat preservative system.
(ii) Description of the Prior Art
Nitrite is an important meat preservative. Its incidental use dates back to ancient times and as early as 3000 BC in Mesopotamia. Presence of nitrate impurities in rock salt (crude sodium chloride) was responsible for much of the curing action. Later it became known that nitrate, through action of bacteria and by post-mortem reducing activity of muscle tissue, was converted to nitrite in the curing process. Regulated use of nitrite, as such, has been practised since the mid-1920's to ensure the safety of products, and to prevent food poisoning. Nitrite has a multifunctional role in the meat curing process. Nitrite is responsible for a reddening effect and development of the characteristic and well-loved flavor of cured-meats. Nitrite with its potent antioxidant properties eliminates the problem of warmed-over flavor development and thus extends shelf-life of cured-meat products. Most importantly, it has bacteriostatic properties which retards germination of spores and formation of the deadly neurotoxin of Clostridium botulinum, amongst others. Cured-meat products have been prepared for many years by treatment of fresh meat with an alkali metal nitrite-containing composition or with a composition containing a mixture of alkali metal nitrite and an alkali metal nitrate. Sodium chloride is always incorporated with nitrite in the curing mixture as well as ascorbic acid, isoascorbic acid (sometimes called erythorbic acid) or their respective salts which have been found to accelerate formation and to increase stability of cured-meat pigments. Other curing adjuncts, such as sugar, spices and polyphosphates are also sometimes present. Conventional alkali metal nitrite or nitrate/nitrite-containing curing mixtures provide quite satisfactory cures in so far as cured meat preservation, flavor and development of pink to red color characteristics of cured meats are concerned. Nitrates were at one time used alone and then one had to depend on bacterial action for their conversion to nitrite during the curing process. No practical single substitute for the nitrite ion in the curing process has yet been discovered.
In the past, many attempts have been made to control bloom (freshness appearance) in red meat. Many methods involved quick freezing and maintenance of freezing temperatures of freshly butchered carcasses or involved methods wherein vitamin C or other antioxidant solutions have been sprayed on red meat or they were dipped in such solutions in order to minimize exposure to oxygen in air. Exposure of oxygen to red meat renders it brown or dark brown in color, after a period of time, thus, leaving it less appetizing in appearance to the consumer than is generally desirable. In meat canning, the product is typically processed by grinding, cutting, chopping or the like and thorough mixing of comminuted meat with seasoning ingredients. The mixed meat, which may be partially cooked, is then placed into a sealed container (referred to hereinafter as a can) and heated to ensure complete cooking and sterilization. Heating results in coagulation and denaturation of meat protein. During cooking and canning processes, in the absence of nitrites and/or nitrates, frequently a color change will occur, typified by formation of a surface discoloration of a greenish nature which gives meat the appearance of being spoiled, even though it is commercially sterile.
For many years, alkali nitrite has been used in production of sterilized canned beef, pork, poultry and fish. Nitrite along with salt and mild-heat treatment produces with respect to red meats, a product with stable pink color and typical cured flavor. Additionally, in non-sterilized products, nitrites inhibit growth of Clostridium botulinum bacteria and production of their toxins during storage. It is generally accepted that stable color produced by using nitrites and nitrates is caused by chemical reactions between nitrates and nitrites and tissue heme pigments of red meat, i.e., myoglobin and hemoglobin. Nitrate and nitrite ions by several intrinsic chemical oxidation and reduction reactions in meat become nitric oxide which reacts with myoglobin to form nitric oxide myoglobin. The latter, on heating, is transformed to nitric oxide myochromogen, a stable pink pigment which provides a pleasing color to meat. Products of this process have gained widespread acceptance amongst consumers.
Unfortunately, use of nitrite has been under considerable pressure for the past 15 years or so due to its possible reactions with amines and amino acids in meats forming carcinogenic N-nitrosamines in certain cured products under high temperatures of pan-frying. Nitrosamines, e.g. N-nitrosopyrrolidine and N-nitrosodimethylamine have been detected at &lt;100 ppb in bacon, which has been cured with conventional curing mixtures, and which has been cooked by methods in which fat reaches relatively high temperatures. These nitrosamines however are generally not found in cured-raw products. Apparently, the temperature attained by fats in frying or equivalent cooking processes, such as broiling, grilling, microwave heating, etc., facilitates reaction of nitrites with amines to form N-nitrosamines. Consequently, methods of cooking, nitrite concentration, salt concentration, pH and presence of reductants are factors determining the potential production of N-nitrosamines. Furthermore, residual nitrite present in cured meats (5-30 ppm) upon ingestion may lead to the formation of N-nitrosamines in the stomach or may act as a cocarcinogen. Carcinogenicity of N-nitrosamines in a variety of experimental animals e.g. rodents, fish etc. has been confirmed. N-nitrosamines are regarded as a potential hazard in human food products. Thus, it is prudent to eliminate precursors of N-nitrosamine formation from curing mixtures and to develop alternatives to nitrite. The National Academy of Sciences has recommended that exposure of N-nitroso compounds to humans from nitrite-cured foods be reduced and strategies for long-term research on alternatives to nitrite usage be developed. Moreover, this is in line with the stated policy of the United States and Canadian governments.
To overcome potentially serious problems, inherent in use of nitrites, several suggestions have been made. Firstly, efforts have been made to reduce the amount of nitrite used in the curing system as well as to develop alternative methods of meat curing. Since rate of N-nitrosamine production depends on the square of the concentration of residual nitrite in meats, a reduction in the level of nitrite addition to meats has proven to be an effective measure in reducing risk of N-nitrosamine formation. In addition, use of N-nitrosamine-blocking agents, e.g. .alpha.-tocopherol together with ascorbates, has been suggested. The N-nitrosamine problem has also led to the removal of nitrate from curing practices in North America, eliminating concern over controlling the reduction rate of nitrate to nitrite. However, the most reliable method as far as N-nitrosamines are concerned, is total elimination of nitrite from the curing process. Since the likelihood of finding a single compound to mimic all functions of nitrite is infinitely remote, efforts in the past were concentrated on developing alternatives which performed a selected function of nitrite.
Color of raw meat is primarily due to the muscle pigment myoglobin which is composed of an iron-porphyrin complex and protein globin. This iron-porphyrin complex or heme gives color to myoglobin as well as to hemoglobin and cytochrome C. The oxidation state of heme iron which binds itself to tetrapyrrole nitrogensatoms in the centre of the porphyrin ring is +2. Axial coordination sites of the iron atom are occupied by the protein globin, through its imidazole ring, and a molecule of oxygen, or water. Reaction of a nitrosating agent with myoglobin produces nitrosomyoglobin or nitric oxide myoglobin which has a bright-red color and is the pigment present in cured meat prior to heat processing. Nitrosomyoglobin is very stable in the absence of oxygen, however in its presence, stability of the pigment is limited by the rate of dissociation of the nitric oxide complex. Since oxygen is believed not to react directly with bound nitric oxide, the complex has a half-life of several hours at room temperature. The final pink color of nitrite cured-meat is due to the cooked cured-meat pigment, [CCMP]. It has been shown that during heat processing, the globin fraction of myoglobin is denatured and may then be replaced by a second nitric oxide molecule. The pathways below represent possible reactions and intermediates involved in the production of the cooked cured-meat pigment from myoglobin and nitrite, where P signifies protein and where hemoglobin may replace myoglobin. ##STR1##
The reactions of myoglobin and hemoglobin with a nitrosating agent are shown below. ##STR2##
Since the characteristic pink color of cured meats has a special role in consumer acceptance, as it is usually associated with quality of processed meats, it is desirable to preserve this color attribute of the product without use of nitrites and nitrates which may form carcinogens. Nitrites and/or nitrates used in canned, heat sterilized meats are obviously not necessary as antibacterial agents, but serve primarily as color preservatives. A large number of colorants to substitute nitrite has been examined to reproduce the color of cooked cured-meat in nitrite-free curing systems. Nicotinic acid, nicotinamide, and their derivatives are examples of compounds that form complexes with myoglobin, or heme compounds, which are similar in color to the pigment in cured meats. Although a number of patents has been granted for these particular substitutes, a common problem has prevented their commercial use. These heme complexes are generally less stable than the nitric oxide complex of cooked cured-meat pigment and as such are more susceptible to oxidation. Furthermore, many of the colorants tested to mimic cured-meat color have toxicity and health-related problems and as such their use in meat processing is undesirable. For instance, substances derived from nicotinic acid are potent vasodilators for small blood vessels. Some of the key patents mentioned above to preserve color of fresh and processed meats are summarized below.
U.S. Pat. No. 2,177,519 provided a neutralizing agent, preferably an innocuous alkali metal salt of a weak acid, e.g., an alkali metal aluminate, to inhibit discoloration of ground or exposed meat due substantially or entirely to the presence of methemoglobin which is formed by oxidation of ferrous hemoglobin in order to preserve the red color of fresh meat and natural flavor thereof.
A process of preserving natural color of fresh meat in U.S. Pat. No. 3,266,909 comprised subjecting the meat to contact with an aqueous solution consisting essentially of water, at least 2.0 wt. percent of gelatin, at least 0.5 wt. percent of a reductant, and at least 2.0 wt. percent of a neutral alkali metal salt of glutamic acid.
The patent teaches that addition of certain .gamma.-pyrones to raw comminuted red meats inhibits change in color which normally takes place during storage of raw ground red meats. In U.S. Pat. Nos. 3,867,588 and 3,867,981, use of several pyrones, namely 3-hydroxy-2-methyl-.gamma.-pyrone and 3-hydroxy-2-ethyl-.gamma.-pyrone, to preserve the red color of raw meat was disclosed. The process specifically required incorporation and thorough mixing of a .gamma.-pyrone into ground meat and subsequent refrigeration for 24 h or more. The patentees stressed that the process involved treatment of fresh, raw, uncured, red meat only and that no cooking took place during the process, noting that cooking brought on a different transformation of color. Curing of meat was not specifically involved in this process.
In U.S. Pat. No. 3,899,600 the patentee taught nitrite-free multicomponent meat curing systems consisting of an antioxidant or a chelator, an antimicrobial agent and a food colorant, e.g. erythrosine in preparation of comminuted products.
The invention in U.S. Pat. No. 3,899,600 involved a meat composition to replace nitrite in the production of comminuted cured-meat products. This composition consisted of ground beef and pork containing water, sodium chloride, sucrose, a colorant (erythrosine), an antimicrobial agent (methyl paraben), and an antioxidant and a sequestrant, namely TBHQ and STPP.
In U.S. Pat. No. 3,966,974, the patentees were concerned with replacing sodium nitrite with organic nitrites.
In U.S. Pat. No. 4,001,446, a process for forming a stabilized red color in an animal protein source containing iron was provided. This process comprised: obtaining at least one animal protein source selected from the group consisting of meat, blood, and a meat by-product; forming a slurry, dispersion, or suspension of the protein source; adding at least one edible reducing agent to the protein source wherein the reducing agent comprises up to 2% by weight of the protein source, and whereby iron content of the protein source was maintained in the ferrous state; agitating the slurry dispersion, or suspension of the protein source; reacting the protein source with carbon monoxide sufficiently to achieve at least 10% saturation to form a retort- and color-stabilized protein source; and recovering the retort- and color-stabilized protein source.
In U.S. Pat. Nos. 4,039,690, 4,076,849, 4,086,561 and 4,088,793, the patentees were concerned with various aspects of control of nitrosamine production in nitrite-cured meats, particularly bacon.
U.S. Pat. No. 4,262,022 provided a process for producing a decolorized edible material from blood by hemolyzing a red blood corpuscle containing blood fraction; then partially hydrolyzing the hemolyzed blood fraction enzymatically with the proteinase of Bacillus licheniformis to a degree of hydrolysis of at least 10, forming thereby a hydrolyzate constituted of a decolorized supernatant containing partially hydrolyzed edible protein dissolved therein and a sludge; and thereafter deactivating the proteinase and recovering the supernatant. Heme compounds were a by-product in this process.
In U.S. Pat. No. 4,279,936, a method for preserving pink meat color in canned, cooked "red" meat, in the absence of nitrites or nitrates, was provided by adding to meat selected quantity of .gamma.-pyrones at one or more of the various stages of curing, cooking and canning processes, and in some instances, also in connection with addition of iron salts was provided.
U.S. Pat. No. 4,293,576 provided a process for producing a food product simulating meat from an anticoagulant-treated, coagulable blood fluid by controlled, chemically-stimulated coagulation of the blood fluid under controlled temperature conditions, by the steps of: coagulating an anticoagulant-treated, coagulable blood fluid, whole animal blood, a plasma phase of animal blood, a mixture of a hemoglobin phase of animal blood and a plasma phase of animal blood, a mixture of whole animal blood and a plasma phase of animal blood; a mixture of whole animal blood and a hemoglobin phase of animal blood or a mixture of whole animal blood, a plasma phase of animal blood and a hemoglobin phase of animal blood, in the presence of an exudation-inhibiting agent and a coagulation stimulant, both present in effective amounts, while maintaining the blood fluid at a temperature within about 10.degree. C., either above or below the physiological temperature of the animal from which blood has been derived to chemically induce coagulation, and then recovering the resultant coagulate.
The patentees, in U.S. Pat. No. 4,599,234, provided compositions for curing meats comprising (di)nitrosyl ferrohemochrome and at least one antioxidant, at least one sequestering agent and at least one antimicrobial agent. Such compositions were said to bestow similar color, flavor, and microbiological stability as that associated with nitrite-treated meats.
The invention in U.S. Pat. No. 4,559,234 involved meat compositions comprising the preformed (di)nitrosyl ferrohemochrome, and at least one antioxidative agent, at least one sequestering agent and at least one antimicrobial agent. Suitable antioxidants included dl-.alpha.-tocopherol, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PG), trihydroxybutyrophenone (THBP), nordihydroguaiaretic acid (NDGA), t-butylhydroquinone (TBHQ), catechol, gum guaiac, lecithin, dilauryl thiodipropionate, ascorbic acid (AA), physiologically acceptable salts of ascorbic acid, erythorbic acid, ascorbyl palmitate, and ascorbyl acetal. Suitable sequestering agents included monosodium phosphate, disodium phosphate, sodium hexametaphosphate (SHMP), sodium tripolyphosphate (STPP), sodium pyrophosphate (SPP), citric acid (CA), monoglyceride citrate, 8-hydroxyquinoline, sodium gluconate, catechol, ethylenediamine tetraacetic acid (EDTA), disodium ethylenediamine tetraacetate (Na.sub.2 EDTA), diethylenetriamine pentaacetic acid (DPTA), and salicylic acid. Suitable antimicrobial agents included sodium hypophosphite (SHP), potassium sorbate and propyl parahydroxybenzoate (propyl PARABEN.TM.), methyl fumarate, dimethyl fumarate, ethyl fumarate, and diethyl fumarate. Of particular interest were compositions comprising (di)nitrosyl ferrohemochrome; antioxidant agents selected from the group consisting of sodium ascorbate, ascorbyl acetal, ascorbyl palmitate, TBHQ, BHA, and BHT; and sequestering agents selected from the group consisting of STPP, SHMP, EDTA and DPTA. Such compositions may comprise (a) (di)nitrosyl ferrohemochrome; (b) an antioxidant; (c) a sequestering agent; and (d) an antimicrobial agent. In such compositions the weight-to-weight ratios were: (b)/(a) below 64 (preferably 2 to 16); (c)/(a) below 160 (preferably about 40) for a non-phosphate sequestering agent and below 1000 (preferably about 240) for a phosphate sequestering agent; and (d)/(a) below 1000 (preferably about 240). Such compositions may be in the form of a premix or kit of components in proportions appropriate for particular applications. The above-mentioned compositions may be mixed with water, with salt and sugar, and with water, salt and sugar.
U.S. Pat. No. 4,746,522 provided a composition for treating meat to reduce moisture loss incurred during cooking by the use of an acetic acid solution, gelatin, starch, sodium chloride, a phosphate salt, and non-halogenated water.